Corrosion of steel in reinforced concrete is a major problem. Both impressed current and galvanic (sacrificial) electrochemical treatments have been used to arrest this problem. In impressed current electrochemical treatment, the anode is connected to the positive terminal and the steel is connected to the negative terminal of a source of DC power. In galvanic electrochemical treatment, the protection current is provided by corroding sacrificial anodes that are directly connected to the steel. A sacrificial anode dissolves in the process of producing the protection current.
Sacrificial anodes for concrete structures may be divided into anodes that are embedded within cavities in the concrete (ACI Repair Application Procedure 8—Installation of Embedded Galvanic Anodes (www.concrete.org/general/RAP-8.pdf)) or anodes that are attached to the concrete surface (U.S. Pat. No. 5,292,411, BS EN 12696:2000) such that they are accessible. Sacrificial anode systems include an anode and a supporting electrolyte.
Sacrificial anodes attached directly to the concrete surface are accessible to facilitate anode replacement. However surface applied anodes often loose adhesion to the concrete surface. Sacrificial anodes are also buried in cavities formed for this purpose. These anodes are strongly attached to the concrete. However they have a small surface area and usually require some form of activation to maintain a high current output. An activating agent may be located in a porous surrounding material or backfill to promote current output. This backfill also provides space to accommodate the products of anodic dissolution. The backfill is weak and is normally separated from a weathering environment by a layer of repair mortar that will typically be 10 mm thick. This results in the need for a relatively deep cavity compared to the anode size in which to install the anode. However the size of the cavity is often limited by the location of the steel reinforcement within the concrete and it is sometimes impractical to install embedded anodes that are distributed within a concrete structure to distribute the protection current to the steel.
The problem to be solved by this invention is to improve the method of attaching sacrificial anode systems to the concrete and to reduce the amount of concrete removed when installing distributed discrete sacrificial anode systems.